FISHERY BULLETIN: VOL. 84, NO. 3 



Table 14.— Estimates of dolphin mortality incidental to U.S. purse seiners, 

 by species and year, from Status of Porpoise Stocks Workshop Report (Smith 

 text footnote 2). Coefficients of variation of totals in parentheses. 



1 Kills of unidentified dolphins prorated among known species. 

 2 Sum of estimated kills over species not exactly equal to total estimated kill because 

 of rounding error. 



contained only one dolphin set. Such small sample 

 sizes within some strata account for the lower preci- 

 sion of the SOPS estimates relative to my estimates. 

 While the differences between my point estimates 

 and those in SOPS are small in a statistical sense, 

 my estimates are consistently lower except for 1976. 

 However, these new estimates are to be preferred 

 on methodological grounds. I tested for statistical- 

 ly significant between-strata differences in mean kill 

 and pooled over strata when significant differences 

 were not detected or when sample sizes were other- 

 wise too small. Pooling of the data produced esti- 

 mates which were more precise than the SOPS 

 estimates because it resulted in fewer strata with 

 larger sample sizes. However, to minimize the 

 possibility of introducing bias into the estimates dur- 

 ing the 1973-76 period, when the sample was un- 

 representative of area and quarter, I did not pool 

 over area and I pooled over quarter only in the event 

 of small sample sizes. 



ACKNOWLEDGMENTS 



I am grateful to K. E. Wallace, C. J. Orange, and 

 G. Ver Steeg for providing data, and to R. G. Punsly 

 for modifying his procedure to estimate numbers of 

 sets for U.S. seiners only. I also appreciate the 

 helpful reviews by two anonymous individuals as 

 well as those by F. G. Alverson, I. Barrett, D. G. 

 Chapman, P. S. Hammond, R. S. Holt, N. C. H. Lo, 

 J. M. Michalski, G. T. Sakagawa, and K.-T. Tsai. 

 Finally, I am especially indebted to T. D. Smith for 

 his suggestions and encouragement. 



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